EFFECTS OF KAOLIN-BASED PARTICLE FILM AND FRUIT ZONE NETTING ON CABERNET-SAUVIGNON GRAPEVINE PHYSIOLOGY AND FRUIT QUALITY

Aims : Long exposure to high temperatures or UV-radiation may induce negative effects on vine physiology and grape composition. Here, the effects of two methods to moderate radiation and temperature in the fruit zone of a Cabernet Sauvignon vineyard were evaluated against a control. Methods and results: The treatments assessed were: (a) periodical spraying of kaolin on leaves and bunches and (b) fruit zone netting with a Raschell's type mesh. The kaolin-based treatment increased the reflectance of light and moderately reduced fruit temperature (similar to 1 degrees C below the control), whilst the shading net caused a significant reduction in radiation and temperature in the fruit zone (similar to 7 degrees C below the control). The Net treatment showed lower (more negative) stem water potential values than the control, but did not persist until the end of the trial. Also, none of the treatments led to significant changes in stomatal conductance, transpiration or CO2 assimilation throughout the season. However, the incidence and severity of fruit dehydration was significantly lower in the treated plants compared to the control. Finally, no differences in fruit chemical composition were observed between the treatments and the control. Conclusion : Under the conditions of this trial, both treatments tested were sufficient in moderating the negative effects of excess radiation or high temperature on grape berries. Significance and impact of the study: Kaolin-based particle spraying and fruit zone netting were proved to be feasible practical alternatives to lessen the negative effects of excess radiation or high temperature on grape berries, under hot climate.